LED current and dimming control using hysteresis comparatoradjustment of hysteresis upper and lower threshold levels

摘要

An LED control circuit is for controlling a current supplied to an LED unit using a comparator circuit for detecting upper and lower thresholds in the output current based on the voltages at each end of a sense resistor. The current is maintained between the thresholds. For this purpose, a reference current source is used for generating upper and lower threshold references. A comparator is used for detecting a mid-range voltage and the reference current source is controlled using this comparator signal thereby to vary the upper and lower threshold references to maintain a constant median or average output current.